The present invention relates generally to catheters systems. In particular, the present invention is directed to a catheter system that provides for the controlled longitudinal movement of an elongate elementxe2x80x94such as a rotatable catheter core with an operative clement, for example an ultrasonic transducer or an optical fiber imaging device, at its distal end, or a drive cable with an atherectomy cutter at its distal endxe2x80x94housed within a sheath positioned within a patient.
Arteriosclerosis, also known as atherosclerosis, is a common human ailment arising from the deposition of fatty-like substances, referred to as atheromas or plaque, on the walls of blood vessels. Such deposits occur in both peripheral blood vessels which feed the limbs of the body and the coronary vessels which feed the heart. When the deposits accumulate in localized regions of a blood vessel, stenosis, or narrowing of the vascular channel, occurs. Blood flow is restricted and the person""s health is at serious risk.
Numerous approaches for reducing and removing such vascular deposits have been proposed, including balloon angioplasty where a balloon-tipped catheter is used to dilate a region of atheroma, and other devices that are pushed or pulled along or through a deposit, such as atherectomy where a blade or cutting bit is used to sever and remove the atheroma, spark gap reduction in which an electrical spark burns through the plaque, laser angioplasty where laser energy is used to ablate at least a portion of the atheroma, and opening of vessels through the use of stents.
Two major difficulties in using such devices are maintaining a constant translational rate for the device and obtaining images of and information on the region of the blood vessel to be treated. Several imaging techniques have been proposed. Catheters incorporating mechanical rotation of ultrasonic transducers for imaging are disclosed in U.S. Pat. Nos. 4,794,931; 5,000,185; 5,049,130; and 5,024,234. These catheters scan in a plane normal to the catheter axis. Catheters employing phased array imaging systems are disclosed in U.S. Pat. Nos. 4,841,977 and 4,917,097. Catheters employing fiber optic imaging components are also known.
Generally deposits extend some longitudinal distance along the length of a vessel. To view different portions of the deposit a physician typically moves a handle attached to a proximal end of the imaging catheter along the vessel, for example, by pushing or pulling the catheter.
Imagining using computer-assisted reconstruction algorithms enables physicians to view a representation of the patient""s interior intravascular structures in two or three dimensions (i.e., so-called three-dimensional or longitudinal view reconstruction). In this connection, image reconstruction algorithms typically employ data-averaging techniques which assume that the intravascular structure between an adjacent pair of data samples will simply be an average of each such data sample. Thus, the algorithms use graphical xe2x80x9cfill inxe2x80x9d techniques to depict a selected section of a patient""s vascular system under investigation. Of course, if data samples are not sufficiently closely spaced, then lesions and/or other vessel abnormalities may in fact remain undetected (i.e., since they might lie between a pair of data samples and thereby be xe2x80x9cmaskedxe2x80x9d by the image reconstruction algorithms mentioned previously).
Even with the most skilled physician, it is practically impossible to manually exercise sufficiently slow constant rate longitudinal translation of the ultrasound imaging device (which thereby provides for a precisely known separation distance between adjacent data samples). In addition, with manual translation, the physician must manipulate the translation device while observing the conventional two-dimensional sectional images. This division of the physician""s attention and difficulty in providing a sufficiently slow constant translation rate can result in some diagnostic information being missed. To minimize the risk that diagnostic information is missed, it is necessary to lengthen the imaging scan time which may be stressful to the patient. Similarly, it is difficult for physicians to manually control the translational rate of atherectomy catheters and other interventional devices that are longitudinally advanced and retracted through blood vessel and other body lumens.
U.S. Pat. No. 5,485,486 discloses an ultrasound imaging transducer which is capable of being translated longitudinally within a section of a patient""s vascular system at a precise constant rate through the use of a longitudinal translation assembly. The longitudinal translation assembly moves the entire rotary drive assembly to provide the desired longitudinal movement of the transducer. Such an ability enables a series of precisely separated data samples to be obtained thereby minimizing (if not eliminating) distorted and/or inaccurate reconstructions of the ultrasonically scanned vessel section (i.e., since a greater number of more closely spaced data samples can reliably be obtained). Also, such an assembly can be operated in a xe2x80x9chands-offxe2x80x9d manner which allows the physician to devote his or her attention entirely to the real-time images with the assurance that all sections of the vessel are displayed. While such a longitudinal translation assembly can work well, it is relatively large, bulky and heavy; it is expensive; and it is cumbersome to set up, in part because the rotary drive and longitudinal translation assemblies are wrapped in separate sterile drapes or barriers (plastic bags) for sterility.
One of the disadvantages with some conventional pullback systems is separate modules are used to provide the rotational and translational movement. These modules require the use of sterile barriers about each. Also, some prior art pullback systems lack the capability to permit the user to manually translate the catheter core to preposition the operative element along the distal end of the catheter core.
The present invention is directed to a driveable catheter system which requires only one sterile drape to be used about a catheter drive unit. The catheter and the pull-back sled preferably include no electrical devices, such as motors, wires, batteries or electrical or electronic components, and can be made to be disposable after a single use. The invention is designed so that user set up and translational movement is simplified. Manual translational movement of the catheter core, with the operative element typically at is distal end, is easy and straightforward. The invention preferably provides translation displacement information on displays carried by both the catheter drive unit and the control unit. The catheter drive unit and the control unit are preferably coupled in a manner to permit two-way communication between the units thus permitting control signal inputs from the control unit as well as the catheter drive unit itself.
The driveable catheter system includes a driveable catheter assembly having a catheter drive unit movably mounted to a catheter drive sled. A catheter extends from the catheter drive unit. Typically the catheter includes an outer sheath, the proximal end of which if fixed in place by the sled, and a catheter core, which is translatable and rotatable within the catheter sheath by the catheter drive unit. A control unit is spaced apart from the catheter drive unit also and preferably provides power for the catheter drive unit. The control unit preferably provides inputs to and receives information from the catheter drive unit.
The sled preferably includes a base having a drive track and drive unit adapter configured for removably coupling the catheter drive unit to the sled base. The sled also preferably includes a sled drive train, one end of which has drive unit interface operably coupleable to the catheter drive unit. The other end of the sled drive train is coupled to the drive track. The drive unit interface preferably has a generally conical drive surface having a bag-piercing tip so that a sterile drape enclosing the catheter drive unit is automatically effectively pierced at the drive unit interface when the catheter drive unit is mounted to the drive unit adapter.
The catheter drive unit preferably includes a housing, a catheter core rotator within the housing and drive unit translator within the housing. The drive unit translator preferably includes a translator drive motor, a translator drive train operably coupling the translator drive motor to a translator drive output. The translator drive output is engageable with the preferably generally conical drive unit interface. The translator drive train preferably includes a user operable clutch for selectively decoupling the translator drive motor from the translator drive output. A translation displacement sensor is preferably located along the translator drive train between the clutch and the translator drive output so that actuating the clutch and manually moving the catheter drive unit along the sled continues to provide accurate translational location information for the user.
Translation displacement information is preferably provided on a display mounted to the catheter drive unit as well as on a display of the control unit. The catheter drive unit preferably includes a display reset button, a rotator drive ON/OFF button, and a translator drive ON/OFF button. The control unit preferably provides for rotator drive on/off input, translator drive on/off input, rotation speed input and translation speed input. The catheter unit drive and the control unit are coupled through a two-way communication link which permits control information to be provided to the catheter drive unit from the catheter drive unit and from the control unit; appropriate communication lines are used to permit operational information and data to be provided by the catheter drive unit to the control unit.
Other features and advantages of the invention will appear from the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawings.